1. Field of the Invention
The present invention relates to a microstructured element. The present invention also relates to a method for producing a microstructured element.
2. Description of the Related Art
Various types of structural minute elements have been used in miniature or precision equipment for various physical purposes. For example, in the technical field of printing machines, a print or ink-jet head incorporated in an ink jet printer or plotter is known as one example of miniature or precision equipment including minute elements. A thermal-type print head of a conventional ink jet printer or plotter generally includes a body with a plurality of channels or grooves, a base secured to the body so as to cover the length of the grooves, a plurality of heating elements arranged on a surface of the base facing toward the body, and a nozzle plate fixed to the body adjacent to the longitudinal ends of the grooves. The body, the base and the nozzle plate are structural minute elements for affecting the flow of ink by the shape or dimension of an ink passage defined in these components, as described below.
A plurality of pressurizing chambers are defined between the grooves of the body, the base and the nozzle plate. The pressurizing chambers are connected to a flow-dividing chamber provided in the body, and ink supplied from an external ink-source flows through the flow-dividing chamber into the respective pressurizing chambers. The nozzle plate is provided with a plurality of nozzles, each of which opens to the respective one of the pressurizing chambers. Each of the heating elements is located at a position corresponding to the respective one pressurizing chamber. The heating element is energized to instantaneously heat the ink held in the corresponding pressurizing chamber, so that the ink is pressurized due to the thermal expansion thereof and thereby discharged through the nozzle aligned to the pressurizing chamber.
In this structure, when the ink held in each pressurizing chamber is pressurized by the energization of the corresponding heating element, some of the ink may flow back to the flow-dividing chamber. Accordingly, in the conventional, thermal-type ink jet printer or plotter, it is required to reduce the back flow of the ink from the pressurizing chambers, by optimizing the dimensions of the pressurized chambers and the nozzles as well as the positions of the heating elements, in order to obtain a sufficient pressure or discharging energy of the ink. The lack of ink discharging energy can make the discharged ink susceptible to an external force, and thereby the ink-discharging performance as well as the printing quality of the ink jet printer may be deteriorated. Further, the back flow of the ink from the pressurizing chambers may deteriorate the response of the ink discharging operation of the print head.
On the other hand, a piezoelectric-type print head of a conventional ink jet printer or plotter generally includes a body with a plurality of channels or grooves, a diaphragm secured to the body so as to cover the length of the grooves, a plurality of piezoelectric elements arranged on the reverse side of the diaphragm away from the grooves, and a nozzle plate fixed to the body adjacent to the longitudinal ends of the grooves. The body, the diaphragm and the nozzle plate are structural minute elements for affecting the flow of ink by the shape or dimension of an ink passage defined in these components, as described below.
The diaphragm is made of a flexible material, and a plurality of pressurizing chambers are defined between the diaphragm, the grooves of the body and the nozzle plate. The pressurizing chambers are connected to a flow-dividing chamber provided in the body, and ink supplied from an external ink-source flows through the flow-dividing chamber into the respective pressurizing chambers. The nozzle plate is provided with a plurality of nozzles, each of which opens to the respective one of the pressurizing chambers. Each of the piezoelectric elements is located at a position corresponding to the respective one pressurizing chamber along the reverse side of the diaphragm.
The piezoelectric element is excited to generate an electrostrictive effect, and thereby actuates or deforms a part of the diaphragm defining the corresponding one of the pressurizing chambers. As the part of the diaphragm is deformed to instantaneously reduce the volume of the corresponding pressurizing chamber, the ink held therein is pressurized and thereby discharged through the nozzle aligned to the pressurizing chamber. The piezoelectric elements are separated from each other and are fixedly supported on a base that, in turn, is securely assembled with the body, so as to eliminate any influence on the other parts of the diaphragm defining the other pressurizing chambers during an ink pressurizing operation.
The pressurizing chambers are normally connected to the flow-dividing chamber through restrictions or orifices provided also in the body. When the ink held in each pressurizing chamber is pressurized by the excitation of the corresponding piezoelectric element, the ink is substantially prevented from flowing back to the flow-dividing chamber due to large fluid resistance at the orifice, and thereby is discharged with a sufficient pressure through the nozzle.
The restrictions or orifices are designed and dimensioned to suitably control the ink flow inside the print head, so as to optimize the ink-discharging performance of the ink jet printer. In this respect, when the cross-sectional area of the restriction or orifice is further reduced and the fluid resistance thereof is further increased, the larger discharging energy of the ink from the pressurizing chamber through the nozzle is obtained. The increased discharging energy of the ink can make it hard for the discharged ink to be affected by an external force and, therefore, the ink-discharging performance as well as the printing quality of the ink jet printer can be improved.
However, the reduction of the cross-sectional area of the restriction or orifice also makes it difficult for the ink to flow from the flow-dividing chamber to the respective pressurizing chamber. As a result, ink may be insufficiently supplied into the respective pressurizing chambers or, otherwise, the time required for sufficiently supplying ink into each pressurizing chamber after the ink is discharged therefrom through the nozzle may be increased, which may deteriorate the response of the ink discharging operation of the print head. Accordingly, it is difficult for the conventional, piezoelectric-type ink jet printer or plotter to ensure both a high printing quality and a quick discharge response.
As another example of miniature or precision equipment including minute elements, in the field of hydro-pneumatic arts, a miniaturized pump unit for ensuring a high precision control of a fluid flow rate, used for, e.g., chemical-analysis or medical purposes, is known. A valveless-type, conventional miniaturized pump unit generally includes a body with a fluid-passage or channel, a diaphragm secured to the body so as to cover the length of the channel, and a plurality of piezoelectric elements arranged on the reverse side of the diaphragm away from the channel in a longitudinal array along the length of the channel. The body is a structural minute element for affecting the flow of fluid by the shape or dimension of a fluid passage defined in the body, as described below.
The channel of the body includes a plurality of expanded areas located in mutually spaced arrangement along the length of the channel. The diaphragm is made of a flexible material, and a plurality of pressure chambers are defined between the diaphragm and the expanded areas of the channel of the body. The channel opens the opposite sides of the body and is connected at respective open ends with an external fluid circuit. Each of the piezoelectric elements is located at a position corresponding to the respective one pressure chamber along the reverse side of the diaphragm.
The piezoelectric element is excited to generate an electrostrictive effect, and thereby actuates or deforms a part of the diaphragm defining the corresponding one of the pressure chambers. As the pair of adjacent parts of the diaphragm are deformed to subsequently reduce and thereafter subsequently increase in the same order the volumes of the corresponding pressure chambers, the fluid in the external fluid circuit is pumped through the channel from one open end thereof to the other in a direction corresponding to the propagating direction of the deformation of the diaphragm parts.
The conventional miniaturized pump unit is properly operated by suitably controlling the sequential deformation of the adjacent parts of the diaphragm. To this end, it is necessary to excite the piezoelectric elements while maintaining an accurate predetermined phase-difference therebetween, which may complicate the control system of the miniaturized pump unit. Also, a plurality of pressure chambers and a plurality of piezoelectric elements are inevitably used, whereby it may be difficult to reduce the dimension of the miniaturized pump unit, as well as the manufacturing cost thereof, to a required level.
Incidentally, there have been certain cases wherein the structural minute elements, such as the body of the print head or of the miniaturized pump, are cut or machined by suitable machine tools, so as to impart desired shapes and dimensions to the minute elements. In this case, it is generally necessary to spend much time in a machining process, to ensure the high accuracy of machining of the minute element, which may reduce the production of the minute element. It is also required to provide a cutting tool with a significant dimensional accuracy and a high mechanical strength, which may increase the manufacturing cost of miniature or precision equipment including the minute element.
It is therefore an object of the present invention to provide a minute element with a high dimensional accuracy, adapted to be incorporated in miniature or precision equipment.
Another object of the present invention is to provide a method of producing a minute element with a high dimensional accuracy, without using a machining process.
Further object of the present invention is to provide an ink-jet head including a minute element, which can ensure high printing quality as well as a quick discharge response when incorporated in an ink jet printer or plotter.
Yet another object of the present invention is to provide a miniaturized pump unit, including a minute element, which can be easily and properly operated with a relatively simple structure, and can facilitate the reduction of dimensions and manufacturing cost to a required level.
Yet further object of the present invention is to provide a method of producing such an ink-jet head or a miniaturized pump unit.
In order to accomplish the above objects, the present invention provides a microstructured element comprising a transparent substrate having a major surface; an opaque layer formed in a certain pattern on the major surface of the transparent substrate; and a microstructured layer formed on or above the major surface of the transparent substrate in a pattern corresponding to the certain pattern of the opaque layer, the microstructured layer including a slanted lateral face extending along an edge of the opaque layer in a direction intersecting the major surface at an oblique angle.
In this microstructured element, the microstructured layer may be made of a photosensitive material.
Also, the microstructured layer may be formed directly on the major surface of the transparent substrate.
Alternatively, the microstructured layer may be formed directly on the opaque layer.
It is preferred that the opaque layer comprises a plurality of opaque strips, and that the microstructured layer comprises a plurality of oblique ribs projecting obliquely from the transparent substrate.
The present invention also provides a method for producing a microstructured element, comprising providing a transparent substrate having a major surface; forming an opaque layer in a certain pattern on the major surface of the transparent substrate; and forming a microstructured layer on or above the major surface of the transparent substrate in a pattern corresponding to the certain pattern of the opaque layer, the microstructured layer being provided with a slanted lateral face extending along an edge of the opaque layer in a direction intersecting the major surface at an oblique angle.
In this method, it is advantageous that forming the microstructured layer on or above the major surface of the transparent substrate includes providing a photosensitive layer entirely on the major surface of the transparent substrate and the opaque layer; exposing the photosensitive layer to light transmitted through the transparent substrate from a back surface opposite. to the major surface at an oblique angle with the major surface; and developing the photosensitive layer.
In this arrangement, developing the photosensitive layer may include dissolving a part of the photosensitive layer, which is not exposed to light in the exposing step, by a developer.
Also, forming the microstructured layer further may include plating the opaque layer to fill a recess formed by developing the photosensitive layer with a plating metal; and removing the photosensitive layer while keeping the plating metal laying above the major surface of the transparent substrate.
The present invention further provides an ink-jet head comprising a body; an ink passage defined in the body, the ink passage including a pressurizing chamber for holding ink; an actuator arranged in association with the pressurizing chamber, the actuator capable of being energized to pressurize the ink held in the pressurizing chamber; a nozzle opening to the pressurizing chamber; and an oblique rib protruding inside the ink passage to lean toward the nozzle.
In this ink-jet head, it is advantageous that the ink-jet head further comprises a microstructured element assembled with the body, the microstructured element including a transparent substrate having a major surface; an opaque layer formed in a certain pattern on the major surface of the transparent substrate; and a microstructured layer formed on or above the major surface of the transparent substrate in a pattern corresponding to the certain pattern of the opaque layer, the microstructured layer including a slanted lateral face extending along an edge of the opaque layer in a direction intersecting the major surface at an oblique angle; and that the microstructured layer comprises the oblique rib projecting obliquely from the transparent substrate.
The oblique rib may protrude inside the pressurizing chamber.
Alternatively, the ink passage may include a plurality of pressurizing chambers and a flow-dividing chamber connected to the pressurizing chambers, and the oblique rib may protrude inside the flow-dividing chamber.
It is preferred that a plurality of oblique ribs are disposed in a mutually parallel side-by-side arrangement in the ink passage.
The present invention yet further provides a miniaturized pump unit comprising a body; a fluid passage defined in the body, the fluid passage including a pressure chamber and inlet and outlet ports connected to the pressure chamber; an actuator arranged in association with the pressure chamber, the actuator capable of being energized to pressurize the fluid in the pressure chamber; a first oblique rib protruding inside the inlet port to lean toward the pressure chamber; and a second oblique rib protruding inside the outlet port to lean toward an open end of the outlet port.
In this miniaturized pump unit, it is advantageous that the miniaturized pump unit further comprises a microstructured element assembled with the body, the microstructured element including a transparent substrate having a major surface; an opaque layer formed in a certain pattern on the major surface of the transparent substrate; and a microstructured layer formed on or above the major surface of the transparent substrate in a pattern corresponding to the certain pattern of the opaque layer, the microstructured layer including a slanted lateral face extending along an edge of the opaque layer in a direction intersecting the major surface at an oblique angle; and that the microstructured layer comprises the first and second oblique ribs projecting obliquely from the transparent substrate.
It is preferred that a plurality of first oblique ribs are disposed in a mutually parallel side-by-side arrangement in the inlet port, and that a plurality of second oblique ribs are disposed in a mutually parallel side-by-side arrangement in the outlet port.